I’ve heard people in close relationships fight. Sadly, I’ve even participated in a few of them. Sometimes, these fights can spill into public. I’ve overheard young couples suggest that their partner might be "on crack" before.
Such suggestions were hardly necessary in the little domestic squabble I (and the entire rest of the subway car) overheard Saturday night: the young couple was loudly fighting over who had smoked a disproportionate amount of their shared stash of crack cocaine.